1. Field of the Invention
The invention relates to a keyboard device, more particularly to a keyboard device that can be produced through a simplified fabrication process and that can be easily assembled.
2. Description of the Related Art
FIG. 1 illustrates a conventional keyboard device that includes a substrate 16, a membrane circuit 15, and a plurality of key units (only one is shown). The substrate 16 is subjected to first and second punching operations (see FIG. 2) so as to form the substrate 16 with a plurality of rectangular punched holes 160, and a plurality of positioning lugs 161. Each of the positioning lugs 161 extends upwardly from one side of a corresponding one of the punched holes 160, and is formed with a positioning hole 162 therethrough. The membrane circuit 15 is provided on the substrate 16 and is formed with a plurality of apertures 151 registered with the punched holes 160 in the substrate 16 to permit upward extension of the positioning lugs 161. Each key unit includes an upright biasing member 14 mounted on a film layer 141 that is provided on the membrane circuit 15 and that is formed with a plurality of through holes 142 registered with the apertures 151 in the membrane circuit 15 to permit upward extension of the positioning lugs 161, a base plate 13 disposed on the film layer 141 and formed with an opening 133 to permit upward extension of the biasing member 14 and opposite positioning protrusions 132 on opposite ends 131 to engage the corresponding positioning holes 162 such that the base plate 13 is positioned on the substrate 16, a key cap 11 disposed above and abutting against the biasing member 14, and a foldable retaining member 12 provided between the base plate 13 and the key cap 11 for retaining the key cap 11 on the base plate 13.
The following are some of the drawbacks of the conventional keyboard device:
1. The substrate 16 must be subjected to the first and second punching operations such that the fabrication process for the conventional keyboard device is relatively complicated. Moreover, referring to FIG. 2, during the first punching operation, black areas (A, B) have to be removed from the substrate 16 such that punched scraps generated during the first punching operation result in waste of material.
2. Since the structural strength of each positioning lug 161 is weakened during the first punching operation, deformation of the positioning lugs 161 resulting from the second punching operation may occur. Consequently, accurate engagement between the positioning lugs 161 on the substrate 16 and the positioning protrusions 132 of the base plate 13 cannot be ensured.
Therefore, the object of the present invention is to provide a keyboard device that can be produced through a simplified fabrication process and that can be easily assembled.
According to the present invention, a keyboard device comprises:
a substrate subjected to a single punching operation so as to form the substrate with a plurality of punched holes, each of which has a first side and a plurality of positioning members, each of which includes an upright first wall portion that extends from the first side of a corresponding one of the punched holes, and a second wall portion that is connected to the first wall portion and that extends parallel to the substrate such that the first and second wall portions cooperate to confine a positioning groove;
a membrane circuit provided on the substrate and formed with a plurality of through holes registered with the punched holes in the substrate, respectively, the through holes permitting the positioning members of the substrate to extend upwardly therethrough, the membrane circuit being provided with a plurality of electrical contacts; and
a plurality of key units disposed on the membrane circuit and assembled on the substrate, each of the key units including
an upright biasing member supported on the membrane circuit and having an actuator registered with a corresponding one of the electrical contacts,
a base plate disposed on the membrane circuit and formed with an opening to permit extension of the biasing member therethrough, the base plate having opposite ends, each of which is formed with an outwardly extending positioning block engaged in the positioning groove confined by a corresponding one of the positioning members of the substrate such that the base plate is positioned on the substrate,
a key cap disposed above the base plate, and
a foldable retaining member provided between the base plate and the key cap for retaining the key cap on the base plate such that the key cap is movable toward and away from the base plate,
the biasing member providing a biasing force for moving the key cap away from the base plate.